Aqueous coating compositions containing acidic copolymers of monoethylenically unsaturated monomers with unsaturated epoxy resin esters, preferably together with aminoplast or phenoplast curing agents are known, as illustrated by U.S. Pat. Nos. 3,536,641, 4,145,323 and 4,151,131. Our said prior application is based on the addition of a water soluble bisphenol polyol to form a mixed ester which increases the solids content and reduces the viscosity of the aqueous coatings, but the properties are subject to improvement. It is known in said U.S. Pat. No. 3,536,641 to have glycols present during esterification, especially bisphenol A, but the reduction of solids and viscosity is excessive. The problem is to maximize desired film properties with minimum reduction in the solids content and viscosity.